a technology demonstrator in preparation for future missions. International cooperation in the form of various payloads and a robotic station is invited by China. Phase I: Orbital missions The first phase entailed the launch of two lunar orbiters, and is now effectively complete. Chang'e 1, launched on 24 October 2007 aboard a Long March 3A rocket, scanned the entire Moon in unprecedented detail, generating a high definition 3D map that would provide a reference for future soft landings. The probe also mapped the abundance and distribution of various chemical elements on the lunar surface as part of an evaluation of potentially useful resources. Chang'e 2, launched on 1 October 2010 aboard a Long March 3C rocket, reached the Moon in under 5 days, compared to 12 days for Chang'e 1, and mapped the Moon in even greater detail. It then left lunar orbit and headed for the Earth–Sun Lagrangian point in order to test the TT&C network. Having done that it completed a flyby of asteroid 4179 Toutatis on 13 December 2012, before heading into deep space to further test the TT&C network. Phase II: Soft landers/rovers The second phase is ongoing, and incorporates spacecraft capable of soft-landing on the Moon and deploying lunar rovers. Chang'e 3, launched on 2 December 2013 aboard a Long March 3B rocket, landed on the Moon on 14 December 2013. It carried with it a lunar rover named Yutu, which was designed to explore an area of during a 3-month mission. It was also supposed to conduct ultra-violet observations of galaxies, active galactic nuclei, variable stars, binaries, novae, quasars, and blazars, as well as the structure and dynamics of the Earth's plasmasphere. Chang'e 4 was launched on 7 December 2018. Originally scheduled for 2015, was a back-up for Chang'e 3. However, as a result of the success of that mission, the configuration of Chang'e 4 was adjusted for the next mission. It landed on 3 January 2019 on the South Pole-Aitken Basin, on the far side of the Moon, and deployed the Yutu-2 rover. Phase III: Sample-return The third phase included a lunar sample-return mission. Chang'e 5-T1 was launched on 23 October 2014. It was designed to test the lunar return spacecraft. Chang'e 5 was launched on 23 November 2020, landed near Mons Rümker on the moon on 1 December 2020, and returned to earth with 2 kilograms of lunar soil on 16 December